WEDNESDAY, Aug. 29, 2018 (HealthDay News) -- Many U.S. Army soldiers who attempt suicide have no prior diagnosis of a mental health issue, new research shows, and such histories may not be a good predictor of a soldier's suicide risk.

"The study is one of few to be able to examine risk of suicide attempt among those without a past mental health diagnosis," said study lead author Dr. Robert Ursano. He directs the Center for the Study of Traumatic Stress at Uniformed Services University of the Health Sciences in Bethesda, Md.

Ursano and his colleagues tracked the medical histories of thousands of enlisted soldiers (not including Guard or Reserve members) who served from 2004 through 2009. Attempted suicide risk factors were similar for soldiers with and without a prior diagnosis of a mental health disorder, the researchers found.

What did seem to raise the odds for suicide attempts?

According to the new data, female soldiers were more at risk than males; younger soldiers were at higher odds than older ones; less educated soldiers face higher risks than more educated service members, and odds for a suicide attempt were especially high during a soldier's first year of service.

Other risk factors included being demoted or late for promotion, or having been in a combat arms or combat medic military occupational specialty.

The risk of suicide attempt was also higher among soldiers with a history of family violence, having been the victim of a crime, or having committed a crime.

"Important times for identifying risk may be present after recent physical injury, family violence or being a victim or perpetrator of a crime," Ursano said in a university news release.

Health issues also seemed key. The study found that soldiers who attempted suicide were more likely to have had at least one outpatient clinic visit in the two months before their attempted suicide, and those with eight or more visits were three to five times more likely to attempt suicide.

Interestingly, combat injury was associated with an increased risk of attempted suicide only among those without a history of a mental health disorder, Ursano's group reported.

Psychiatrists weren't overly surprised by the finding that a soldier's history of mental illness wasn't a big predictor of suicide risk.

"The ability to predict suicidal acts or behavior has been found historically to be quite limited worldwide, and there is evidence that military services members are especially vulnerable due to their exposure to increased, variable stressors," noted Dr. Shawna Newman, of Lenox Hill Hospital in New York City.

Dr. Brian Keefe is a psychiatrist and medical director at Zucker Hillside Hospital in Glen Oaks, N.Y. Reviewing the study, he said that "suicide is a complicated, multifactorial problem. The significant percentage of soldiers with no psychiatric diagnosis who attempt suicide shouldn't surprise any mental health clinician who routinely works with suicidal patients."

He also stressed that lack of a prior diagnosis does not necessarily mean that mental health issues weren't there.

"Estimates in civilian populations suggest that somewhere between 40-50 percent of people with psychiatric disorders don't receive any treatment at all," Keefe said.

And because members of the military are trained to "wear both physical and psychological armor" as they defend the United States, they may be even more reluctant to seek out mental health services than civilians are, he reasoned.

Finally, Keefe said, "there is a growing body of literature demonstrating that most complete suicides are impulsive in nature -- that the time between decision to kill oneself and action may be minutes, not hours or days."

So, efforts to "suicide-proof" the living environment might be key to preventing suicidal thoughts from becoming suicidal acts, Keefe said.

"From nets on bridges, to home safes for unloaded weapons, to breakaway closet and shower rods in college dorms, all members of society -- not just doctors -- can take steps to reduce the rising suicide rate," he said.